1. Sustainable Ecosystems
UNIT 1
Sustainable Ecosystems
Chapter 1: Nutrient Cycles and Energy Flow
Chapter 2: Populations and Sustainable Ecosystems
Chapter 3: Biodiversity

2. Nutrient Cycles and Energy Flow
CHAPTER 1
In this chapter, you will:
explain that life depends on recycled matter
describe the processes of photosynthesis and cellular respiration
explain how humans can affect the cycles of matter and energy flow in ecosystems
assess the impact of fertilizers on aquatic ecosystems
observe the chemistry of photosynthesis
model acid precipitation
determine the impact of excess fertilizers on plants
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3. How Disturbed is Too Disturbed?
(Page 5)
If you consider an ecosystem to be similar to a pile of interlocking blocks, how does the removal of blocks from different parts of the pile affect the structure of the “ecosystem” as a whole?
How might an actual ecosystem behave differently than the pile of blocks?
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4. 1.1 Sustainability
(Page 7)
An ecosystem is described as being all the interacting parts of a biological community and its environment.
A sustainable ecosystem is one that is capable of withstanding pressure and giving support to a variety of organisms.
As noted by the Easter Island example on page 7 of the text, humans have the potential to inflict catastrophic changes on an ecosystem. These changes can greatly affect an ecosystem’s sustainability.
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5. Ecosystems and Survival
(Page 8)
All organisms require sustainable ecosystems for their survival. Many organisms depend on more than one ecosystem to survive.
The range of the Ruby-throated hummingbird covers a good portion of North America and a variety of different ecosystems.
The Sargasso eel encounters many ecosystems as it moves from the Sargasso Sea to the Great Lakes.
As demonstrated by the examples above, some organisms encounter a variety of different ecosystems as they live their lives.
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6. Parts of an Ecosystem Every ecosystem has biotic and abiotic parts.
(Page 9)
Every ecosystem has biotic and abiotic parts.
Biotic refers to the living parts of an ecosystem (including plants, animals, and micro-organisms).
Abiotic refers to the non-living parts of an ecosystem (including water, oxygen, light, nutrients, and soil).
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7. Biotic Interactions in an Ecosystem
(Page 10)
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8. Biotic Interactions in an Ecosystem
(Page 10)
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9. Abiotic Characteristics of an Ecosystem
(Page 12)
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10. Abiotic Characteristics of an Ecosystem
(Page 12)
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11. Cycling of Matter and Earth’s Spheres
(Page 13)
Ecological processes move matter from the biotic and abiotic parts of an ecosystem and back again in continuous cycles.
The lithosphere is the hard part of Earth’s surface.
The hydrosphere is all of the water found on Earth (lakes, oceans, and ground water).
The atmosphere is the layers of gas above Earth’s surface.
The biosphere is the regions of Earth where living organisms exist.
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12. Nutrient Cycles: Water
(Page 14)
Nutrients are chemicals that are needed by living things and are continually cycled through ecosystems.
The water cycle moves water through the hydrosphere, atmosphere, and lithosphere. This occurs by way of evaporation, condensation, and precipitation.
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13. Nutrient Cycles: Carbon
(Page 15)
The carbon cycle moves carbon through all of Earth’s spheres. Carbon exists as a gas—carbon dioxide (CO2)—in the atmosphere. This gas is used by plants to make sugars. Sugars are broken down by organisms to release energy and CO2. Carbon is stored in fossil fuels buried within Earth and in carbonate (CO3) rock found in the lithosphere.
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14. Nutrient Cycles: Nitrogen
(Page 16)
The nitrogen cycle moves nitrogen through Earth’s spheres. Nitrogen gas (N2) from the air is converted into ammonium (NH4) and into nitrates (NO3) by bacteria and cyanobacteria.
In terrestrial (land based) ecosystems, ammonium (NH4) is produced by soil bacteria. In aquatic (water based) ecosystems, NH4 is produced by cyanobacteria. Nitrates (NO3) are produced from ammonium.
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15. Nutrient Cycles: Phosphorus
(Page 17)
The phosphorus cycle moves phosphorus from the lithosphere, where it is stored in rocks as phosphate (PO43-), to the hydrosphere by the processes of leaching and run-off. Plants then use the phosphorus.
The phosphates in plants and animals are released back into the soil by bacterial decomposition.
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16. Click the “Start” buttons to review the various nutrient cycles.
Nutrient Cycle Review
Click the “Start” buttons to review the various nutrient cycles.
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17. Human Activities and Nutrient Cycles
(Page 18)
Aquatic ecosystems suffer when run-off contains high amounts of agricultural fertilizers (which are high in nitrates and phosphates). The added nutrients can lead to the eutrophication of bodies of water.
Eutrophication is a process in which nutrient levels in aquatic ecosystems increase, leading to an increase in the populations of primary producers, such as algae.
Eutrophication eventually leads to a reduction in the oxygen content of the water.
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18. Science and Social Policy
(Page 19)
Both Canada and the United States have signed the Great Lakes Water Quality Agreement to help to “restore and maintain the chemical, physical, and biological integrity of the waters of the Great Lakes Basin Ecosystem.”
Environmental farm plans and by-laws have been developed to decrease the amount and number of chemicals that enter Canadian waterways from Canadian farms.
The satellite image above shows an algal bloom in the western basin of Lake Erie which was caused by elevated nutrient levels.
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19. Concepts to be reviewed:
Section Review
(Page 20)
Concepts to be reviewed:
Why do we want ecosystems to be sustainable?
How does matter, including nutrients, move through Earth’s spheres?
How can human activities increase the nutrients entering terrestrial and aquatic ecosystems? What effect do the nutrients have?
What decisions and/or actions can be taken to protect the health of ecosystems?
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20. 1.2 The Biosphere and Energy
(Page 21)
Nuclear reactions in the Sun are the energy source for almost all life on Earth.
The energy received from the Sun warms Earth’s atmosphere and makes Earth habitable. The conversion of solar energy to chemical energy, in the form of food, is carried out by plants, algae, and some bacteria, through the process of photosynthesis.
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21. What Happens During Photosynthesis?
(Page 22)
In the process of photosynthesis, the chlorophyll in plant leaves uses solar energy to assemble glucose molecules from water and carbon dioxide. Oxygen is also produced during the process.
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22. Reviewing Photosynthesis
Click the “Start” button to review the process of photosynthesis.
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23. Sources of Oxygen
(Page 23)
In addition to producing a form of chemical energy that can be used to sustain plants and animals, photosynthesis continuously adds oxygen (O2) to the atmosphere and removes carbon dioxide (CO2).
On a global basis, phytoplankton in the oceans is the biggest contributor to the production of oxygen.
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24. Trophic Levels
(Page 24)
A trophic level is a category of organisms that is defined by how the organisms gain their energy. Energy moves from one level to the next.
Primary producers are organisms that make their own food. Consumers must eat other organisms to get the food (matter and energy) they need to survive.
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25. Trophic Efficiency
(Page 25)
An energy or biomass pyramid shows how the energy stored in biomass at one trophic level moves from the bottom to the top of a food chain.
Biomass is the total mass of living organisms in a defined group or area.
Trophic efficiency is a measure of the amount of energy or biomass transferred from one trophic level to the next higher trophic level.
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26. Trophic Level Virtual Lab
Click the “Start” button to review the interactions between different trophic levels and the transfer of energy through an ecosystem.
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27. Water Pollution and Bioaccumulation
(Page 26)
Bioaccumulation is a process in which materials, especially toxins, are ingested by an organism at a rate greater than they are eliminated.
The level of toxins such as DDT (dichloro-diphenyl-trichloroethane) and PCBs (polychlorinated biphenyls) is highest in the highest trophic levels.
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28. Reviewing Bioaccumulation
Click the “Start” button to review bioaccumulation.
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29. Concepts to be reviewed:
Section 1.2 Review
(Page 27)
Concepts to be reviewed:
Where does the biosphere get the energy it relies on?
How does photosynthesis convert solar energy into chemical energy?
How does energy move from one trophic level to the next?
How can bioaccumulation and biomagnification negatively affect organisms?
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30. 1.3 Extracting Energy from Biomass
(Page 28)
Although not all organisms undergo photosynthesis, all organisms—from single-celled bacteria to complex, many-celled life forms—get energy from glucose.
Cellular respiration is a process that releases energy from organic molecules, especially carbohydrates, in the presence of oxygen.
Fermentation also releases energy but in the absence of oxygen.
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31. Extracting Energy from Food
(Page 29)
In cellular respiration, organisms take in oxygen, which reacts with the glucose in cells to produce carbon dioxide, water, and energy.
During the day, plants produce glucose through photosynthesis. At night and during the day, plants extract energy from the glucose using the process of cellular respiration.
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32. Reviewing Photosynthesis and Cellular Respiration
Click the “Start” button to review the connection between photosynthesis and cellular respiration in plants.
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33. Carbon Dioxide and Other Greenhouse Gases
(Page 29)
Greenhouse gases are atmospheric gases that prevent heat from leaving the atmosphere, thus increasing the temperature of the atmosphere. The greenhouse effect is the warming of Earth as a result of increased greenhouse gases that trap heat energy that would otherwise leave Earth.
Carbon dioxide (CO2) is the most common of the greenhouse gases.
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34. Biomass and Fossil Fuels
(Page 30)
Because fossil fuels come from biomass that was produced by photosynthesis millions of years ago, burning them has an effect very similar to cellular respiration. They both produce large quantities of carbon dioxide (a greenhouse gas) that may contribute to global warming.
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35. Reducing Carbon Dioxide in the Atmosphere
(Page 31)
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36. Fermentation, Methane, and Landfills
(Page 32)
Methane (CH4) is produced by bacteria when they break down organic waste using fermentation. Landfills, dumps, and swamps can produce large amounts of methane.
Methane produced by bacteria in landfills can be captured, processed, and then burned to generate electricity for use in homes and businesses.
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37. Acid Precipitation
(Page 33)
In addition to producing greenhouse gases when burned, fossil fuels also produce undesirable compounds such as nitrogen oxide (NOX) and sulphur dioxide (SO2) that combine with water in the air to form nitric and sulphuric acid. These compounds contribute to acid precipitation, which is rain, snow, or fog that has a pH less than 5.6.
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38. Measuring pH
(Page 34)
A substance’s pH is an indication of how acidic or basic it is. The pH scale ranges from 0 to 7. Substances with a pH:
lower than 7.0 are considered acidic
equal to 7.0 are considered neutral
greater than 7.0 are considered basic
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39. Effects of Acid Precipitation
(Page 34)
Continued exposure to acid rain can remove soil nutrients such as calcium and increase the level of soil nutrients such as aluminum. These changes can lead to the death of trees and, thus, the loss of forests.
Acid precipitation is even more devastating to aquatic ecosystems. Many aquatic organisms have a very low tolerance to changes in the pH of the water they live in.
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40. Reducing Acid Precipitation
(Page 35)
Acid precipitation remains a problem, but the situation seems to be improving. Agreements between Canada and the United States plus new laws have reduced the level of cross-border pollutants. Through the use of scrubbers to remove undesirable gases from industrial emissions and with higher standards for motor-vehicle emissions, acid precipitation has been reduced since the 1980s.
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41. Concepts to be reviewed:
Section 1.3 Review
(Page 36)
Concepts to be reviewed:
How do organisms use cellular respiration and fermentation to extract energy from glucose?
How has the burning of fossil fuels affected the concentrations of greenhouse gases in the atmosphere?
What is acid precipitation? What causes it? How does it affect living things?
What measures have been taken to reduce acid precipitation?
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